1. Field of Invention
This invention relates to ink jet printing systems and methods.
2. Description of Related Art
Continuous stream or drop-on-demand liquid ink printers, such as piezoelectric, acoustic, phase change wax-based or thermal printers, have at least one printhead from which droplets of ink are directed towards a recording medium. Within the printhead, the ink is contained in at least one channel, or preferably in a plurality of channels. Power pulses cause the droplets of ink to be expelled as required from orifices or nozzles at the end of the channels.
In a thermal ink-jet printer, the power pulse is usually produced by a heater transducer or resistor, typically associated with one of the channels. Each heater transducer or resistor is individually addressable to heat and vaporize ink in one of the plurality of channels.
The ink jet printhead may be incorporated into either a carriage type printer, a partial-width-array type printer, or a page-width type printer. The carriage type printer typically has a relative small printhead containing the ink channels and nozzles. The printhead can be sealingly attached to a disposable ink supply cartridge. The combined printhead and cartridge assembly is attached to a carriage, which is reciprocated to print one swath of information at a time on a stationary recording medium, such as paper or a transparency. Each swath has a width equal to the length of a column of nozzles. After each swath is printed, the recording medium is stepped a distance equal to the height of the printed swath or a portion of the swath, so that the next printed swath is contiguous or overlapping with the previously printed swath. This procedure is repeated until the entire page is printed.
The page-width printer includes a stationary printhead having a length sufficient to print across the width or length of a sheet of recording medium at a time. The recording medium is continually moved past the page width printhead in a direction substantially normal to the printhead length and at a constant or varying speed during the printing process. A page width ink-jet printer is described, for instance, in U.S. Pat. No. 5,192,959.
Many liquid inks, and particularly those used in thermal ink jet printing, include a colorant or dye and a liquid, which is typically an aqueous liquid vehicle, such as water and/or a low vapor pressure solvent. The ink is deposited on the recording medium to form an image in the form of text, graphics and/or pictures. Once deposited, the liquid component is removed from the ink and the recording medium to fix the colorant to the recording medium by either natural air drying or by active drying. In natural air drying, the liquid component of the ink deposited on the recording medium is allowed to evaporate and to penetrate into the substrate naturally without mechanical assistance. In active drying, the recording medium is exposed to heat energy of various types, which can include infrared heating, conductive heating and heating by microwave energy. Active drying of the image can occur either during the imaging process or after the image has been made on the recording medium.
Natural air drying and active dryer each have an operating range. That is, natural air drying and active dryer are not able to dry more than a certain amount of ink per unit of time, called the "ink drying rate". The ink drying rate depends from the humidity and the temperature of the ambient air.